The present invention relates generally to amusement machines having rotating reel assemblies, and specifically to coin-operated slot machines of the type found in Monte Carlo, Reno, and other internationally known gaming resorts.
A major factor in the design of slot machines and other rotating reel devices is their ability to withstand the stress of repeated impact loading caused by rapid acceleration and deceleration of the reel assemblies. Rapid changes in reel speed subject these machines to forces which cause fatigue and/or failure in structural members. In addition, such acceleration intensifies surface friction and grinding between moving parts, creating shavings and other abrasive particles which spread throughout the machine and decrease the useful life of bearings, solenoids, and other parts having opposed moving surfaces to which the debris is carried. Accordingly, frequent repair and maintenance is required, resulting in high servicing costs.
The profitability of these machines is further reduced by the percentage of "down time" required for servicing, during which the machine produces no revenue. This is particularly true in the case of slot machines and the like, in which multiple rotating reel assemblies and their associated driving mechanisms create a maze of interlocking mechanical elements which may require hours of disassembly to reach an affected part. Extensive disassembly often necessitates removal of the machine from the premises, increasing the cost of repair and associated down time.
Prior attempts to address these problems have not always been entirely successful. One such attempt involved the use of multiple plug in/plug out modules in a slot machine, permitting removal of a single faulty module without disassembling the entire machine. The faulty module could be replaced with a spare during servicing, thus reducing down time and simplifying periodic maintenance or repair.
An example of such a module is seen in U.S. Pat. No. 3,910,582, in which a single reel assembly is rotatably mounted to a removable plate, along with its associated starting and stopping mechanisms. The reel assembly is started and stopped by electrical signals received through mating connector plugs mounted on the module plate and on the machine. Each module has a motor for spinning its associated reel, and an indexing disk having notches about its periphery which are engaged by a stop solenoid to stop the spinning reel when power to the motor is cut off. A resistor ladder network is connected to contact points mounted in two concentric circular arrays on the indexing disk, establishing a different resistance associated with each rotational position of the reel. A pair of electrical wipers couple the contact points to the connector plug so that the reel position may be sensed by external circuitry after the reel has stopped spinning, and a determination made of whether the new reel positions of the various modules display a winning combination.
While such an arrangement allows relatively rapid replacement of a single module for cleaning or repair, this configuration has not met with considerable success. Modular units of this construction are not well suited for use with a large reel having many rotational stopping positions, because the acceleration and deceleration of large reels creates an unacceptable level of strain and structural failure in the modules, thus defeating their intended purpose of simplifying repair and reducing down time. Such modules are also expensive to make, and, with respect to most slot machines, are so large and heavy that a serviceman cannot carry many modules with him at one time.
Another drawback of existing slot machines has been the expense and complexity of mechanisms for starting and stopping reel rotation. In the past, these mechanisms have generally fallen into two categories. The first uses a spring-loaded pawl arm engaging a sprocket to rapidly spin the sprocket and its attached reel when the starting lever is pulled, and a spring-loaded or solenoid actuated stop lever which engages one of the sprocket teeth to rapidly stop the reel at a position where one of its indicia is displayed at the "center line" of a viewing window. These mechanisms require precise alignment of the pawl arm and the stop lever in order to accurately engage the sprocket teeth, involving a complex assembly of inter-related mechanical parts. Such assemblies require regular maintenance, since the jarring action of starting and stopping the reel assembly may disturb the relative alignment of the pawl arm and stop levers.
The second type of mechanism which has been used for controlling reel rotation in slot machines couples each reel assembly to an electric motor when the starting lever is pulled, and stops the assembly with a solenoid engaging a notch in an indexing disk, as in the above described U.S. Pat. No. 3,910,582. While these systems do not present the same alignment problems of the above dual arm mechanisms, they are subject to comparable drawbacks related to player satisfaction and high cost.
Slot machine players have generally developed a preference for the sound, feel, vibration and rapid reel acceleration which is provided by a spring-loaded pawl type starting mechanism. In order to simulate the acceleration of pawl mechanisms, high-torque motors must be used, especially in machines having a large reel with high rotational inertia. Such motors are large, heavy, expensive, and have high current draw especially during the initial period when the reel is accelerating rapidly from rest to full speed. Accordingly, the high cost of manufacture, electricity, and installation of adequate wiring, along with customer preference for the sound and feel of pawl type mechanisms, create significant disincentives to the use of electric motors. Also, the above-mentioned environment inside such machines exposes the motors to abrasive particles which rapidly wear out motor bearings, requiring regular maintenance.
In addition to the above problems of reel starting and stopping mechanisms, design problems specific to reel assemblies have arisen due to the shearing force and abrasive wear to which these assemblies are subjected, especially during deceleration. Reel assemblies having a reel mounted in a frame for rotation with a sprocket or indexing disk are well known as a means for translating the motion of a pawl arm to rotary motion for turning the reel, and for abruptly stopping this rotation by engaging the sprocket or indexing disk with a lever pivotally mounted to the machine frame. However, this abrupt stopping motion creates extremely high stress in the reel assembly and frame, especially where a large diameter reel having high rotational inertia is used. This has required manufacturers of such machines to either limit the size of their reels or use expensive, high strength alloys.
While some attempts have been made to address this problem, they have not been entirely successful. For example, U.S. Pat. No. 4,239,225 discloses a reel stopping mechanism for a reel assembly having an indexing disk fixedly mounted to the reel. The reel stopping mechanism comprises a stop lever pivotally mounted at one end to a fixed point on the supporting frame, the other end having a pin for engaging the notches of the indexing disk to stop the reel assembly. The stop lever's middle portion is designed to enable the lever to extend and retract, and is spring-loaded to hold the lever in its fully retracted position. A stop solenoid pivots the lever into and out of engagement with the notches of the indexing disk. As the lever engages the rotating disk, its spring-loaded middle portion extends to help absorb the impact, then retracts to its original position. While this configuration helps reduce stress loads on the reel and frame, it is expensive to manufacture and subjects the solenoid to sharp lateral forces. This may cause erratic solenoid operation due to excessive wear and binding, resulting in a stopping action which is not consistently timed. It is therefore unsuitable for applications where precise timing of the stop lever is necessary to stop the reel assembly at a predetermined position.
A related problem to the above-mentioned drawbacks of slot machines and the like has arisen in conjunction with the operation of solenoids in an environment where foreign particles may lodge between the solenoid body and the plunger, causing wear, sluggish operation and intermittent binding. This is a particular problem in applications where timing of the solenoid movement is critical, as where the solenoid's activation is timed to control the engagement of two relatively moving objects. In such cases, very small accumulations of debris may cause conventional solenoids to misfire, requiring frequent servicing to clean or replace the solenoid.
Existing solenoids also require that design accommodations be made to permit unrestricted axial movement of the plunger, since pressure lateral to the solenoid axis results in binding and wear between the plunger and solenoid body. These problems are commonly addressed by cutting a slot in the arm to which the plunger is attached, so that a pin connecting the plunger and arm may ride in the slot to relieve lateral pressure. However, such slots typically require machining operations which are expensive and time-consuming. Furthermore, friction between the connecting pin and slot may still cause lateral pressure sufficient to bind the plunger, especially where the only other force on the plunger is the relatively weak pull of the solenoid coil.
While some solenoids have addressed this problem by providing pivotable plungers, these devices are capable of only very limited application. For example, the above-mentioned U.S. Pat. No. 4,239,225 discloses a solenoid, coupled to its stop lever, having a plunger which is pulled axially out of the solenoid body after the coil is de-energized, and then laterally pivots at the end of its stroke to permit the stop lever to extend in a direction perpendicular to the solenoid axis. This feature is only effective for mechanisms in which the plunger head describes an L-shaped movement. It also does not provide a structure which reduces surface friction and binding between opposed solenoid surfaces.
In addition to problems relating to cost and mechanical integrity, prior art slot machines have the common drawback that their operation is excessively repetitive, involving almost no thought or imagination on the part of the player. A player who simply repeats the process of depositing a coin, pulling the handle, and watching for a winning combination on the center line rarely finds enough stimulation to command his attention for long periods of time. Since a payout is the only thing which interrupts this cycle, the machine odds must be set to provide payouts often enough to maintain the average player's interest, decreasing the amount of revenue available to the owner of the machine. A slot machine which offered a player a choice between repetitive "coin pumping" and other playing formats would more actively involve him in the game playing process, reduce the level of boredom in periods between winning payouts, and generally increase user enjoyment, enabling the owner of the machine to set more favorable odds without a corresponding offset in player enthusiasm.